We report the unique phase behavior and structural transitions in thin films of a distorted network (DNW) nanostructure, which is an equilibrium phase contained in the bulk of a nearly-symmetric deuterated polystyrene-block-poly (methyl methacrylate), dPS-b-PMMA, block copolymer. The DNW is due to a broad dispersity for the PMMA block. Grazing incidence small-angle X-ray scattering, neutron reflectometry, atomic force microscopy and transmission electron microscopy techniques were used to characterize thermally-annealed dPS-b-PMMA ultrathin films with neutral boundaries at both the free surface and substrate interface. Brief thermal annealing imposed on the ultrathin films leads to perpendicular lamellae (L⊥). Upon increasing the duration of thermal annealing, the dPS-b-PMMA ultrathin films exhibit thickness dependence of phase transition kinetics and different irreversible routes of phase transition. As a result, the protracted thermal annealing of the thin films of various thicknesses produces either hexagonal arrays of perpendicular PMMA cylinders (HEX-C⊥) or disordered PMMA nanostructures (DIS). The phase transition routes and kinetics in ultrathin films suggest various possibilities to obtain diverse nanoscale patterns via thin film self-assembly.
|出版狀態||已出版 - 1 12月 2020|
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